QHY268C Capture Area Discrepancy

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outdegree
Posts: 2
Joined: Thu Sep 02, 2021 11:30 pm

QHY268C Capture Area Discrepancy

#1

Post by outdegree »

Hello,

I found that "Live View" and "Still Mode" show different available capture resolutions for my QHY268C. I noticed this when my stacking software (PixInsight) threw an error that my darks's geometry did not match my lights.

Sure enough, I captured my lights when "Live View" was enabled (I use it for framing, etc and then just hit "Start Capture"). The day later I was taking darks but I used a new (to me) "Deep Sky" mode/planner in "Capture". The first step in the planner disables "Live View" for "Still Mode". This is when my camera's "Capture Area" changes.

It looks to me that "Still Mode" with QHY268C is disabling the QHY's inactive overscan areas on the sensor whereas "Live Mode" includes the overscan.

Live mode options:
Live-Mode.jpg
Live-Mode.jpg (912.54 KiB) Viewed 693 times
Still mode options:
Still-Mode.jpg
Still-Mode.jpg (922.58 KiB) Viewed 693 times
Found this with 4.0.8138.0.

Thanks,
Sebastian.
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Re: QHY268C Capture Area Discrepancy

#2

Post by admin »

Hi Sebastien,

basically you are correct - in still mode although you can get an image from the camera that includes the overscan area, the data in that border zone of the image is junk, and that junk data seems to upset stacking software, hence SharpCap cutting off that area in still mode.

In live mode, the whole frame provides good data. I must admit that I haven't tried disabling the overscan area in live mode - I have no idea if it is possible or not (or can be done reliably if it is possible). I will investigate.

cheers,

Robin
outdegree
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Joined: Thu Sep 02, 2021 11:30 pm

Re: QHY268C Capture Area Discrepancy

#3

Post by outdegree »

Thank you Robin for looking into this!

I think an on/off button for the overscan area would be a good solution (saw it in QHY's ASCOM drivers). Unless QHY's SDK does not have such capability in their API... :P

Cheers,
Sebastian.
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Re: QHY268C Capture Area Discrepancy

#4

Post by admin »

Hi Sebastien,

that might work if I default overscan to off and it can be applied in both live and still mode, so that the resolution is the same in both modes. You can do most things like that with the SDK, but it is often an interesting game of trial and error to get it to work correctly ;)

cheers,

Robin
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vichman
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Joined: Mon Jun 18, 2018 7:05 am

Re: QHY268C Capture Area Discrepancy

#5

Post by vichman »

Hi Robin,

I have the same issue, with both my QHY268C and QHY600M.
Is there an update to this topic?

Thanks,
Stefan
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Re: QHY268C Capture Area Discrepancy

#6

Post by admin »

Hi,

to be honest, I had forgotten about this, but I have just investigated now.

As far as I can tell there is no way to make this happen in a useful way on QHY cameras :(

* There is a way to tell the camera to 'ignore the overscan area' - my 294C claims not to support that option, and nothing happens if I try to set it ignoring the fact that it may not be supported

* There is a horizontal offset of 16 pixels between live view mode and still mode on my camera - I have no idea if other models have the same offset or not, so I cannot assume a constant 16 pixel offset

* If I force live view into the same resolution as still mode, the offset of 16 pixels remains. I was kind of hoping that it would lock to the same sensor area used in still mode, but that isn't the case.

* If I let still mode use the same resolution as live mode, then there is an offset of 20 pixels horizontally and 28 pixels vertically between the two output images (working again from hot pixel patterns). There is junk data (overscan) at the top and left of this sort of image.

In summary, I can't see any robust way of getting the same resolution out of the two modes and being sure that the images taken in different modes align to pixel accuracy (hot pixels line up) accross the whole range of cameras.

Sorry,

Robin
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vichman
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Re: QHY268C Capture Area Discrepancy

#7

Post by vichman »

Hi Robin,

thanks for looking into this.

QHY's datasheet gives the following resolutions for the QHY268C:
Effective pixel area: 6280 x 4210
Usable max resolution: 6252 x 4176

If I connect the QHY268C e.g. in NINA via the native driver (as in SharpCap), there is a button where I can toggle between the "effective pixel area" and the "usable max resolution". I assume that the "ignore the overscan area" does exactly do that.

Your QHY294C seems to be a particular case, as for this camera the effective pixel area and the usable max resolution seems to be the same.
I checked the QHY website, and there is only the 4164x2796 mentioned, and on Baader Planetarium's website there is a remark on that topic (red box): https://www.baader-planetarium.com/en/q ... amera.html

Would it be possible to implement that switch "ignore the overscan area" in SharpCap?
I would be happy to do beta tests with both the 268C and the 600M cameras.

Thanks
Stefan
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Re: QHY268C Capture Area Discrepancy

#8

Post by admin »

Hi Stefan,

SharpCap already sets the CAM_IGNOREOVERSCAN_INTERFACE option to 1 for all cameras that support that option (and for those that don't to be honest too). I'm not sure if turning that off is the solution or not... The trouble is there are so many ways to get the size of the QHY sensor...

GetQHYCCDChipInfo
GetQHYCCDEffectiveArea
GetQHYCCDOverScanArea

For some cameras it works to use the results from one of these functions, for other cameras the same function will return a size of 0x0 and you need to use the result of another one :(

If you could send me a log of you starting your camera first in live mode then in still mode, I will see if there is anything in the log that I might have missed previously - because of all the confusion, a lot of stuff goes into the log about QHY frame sizes...

Just because the QHY web site says the 294C has one image size, doesn't mean it's true... in video mode the default size is 4164x2822!

cheers,

Robin
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vichman
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Re: QHY268C Capture Area Discrepancy

#9

Post by vichman »

Hi Robin,

I created a log file, unfortunately the file is too large (1,3MB).
Can I send it to you by email?

CS
Stefan
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